Under that $19 billion plan, the MX -- a new-generation intercontinental ballistic missile capable of carrying 10 nuclear warheads -- was to be placed in silos that now house older, less powerful missiles.

The administration official said the plan was dropped in large part because of a belief that because of the increased accuracy of Soviet missiles, hardening the silos would not ensure that the MX could survive a nuclear attack -- a criticism of the interim deployment plan leveled soon after it was announced.